The 3rd dimension exists only as a slice through our concept of time. An animal perceives 2 dimensions in space, the 3rd dimension being perceived as time! The illusory change in shape of the circle of paper from the animal’s point of view is admittedly difficult to swallow, but before dismissing it out of hand please bear with me for some fascinating evidence from previously blind people who describe their world after regained their sight.
The 3rd dimension in space is a solid. In the same way that a surface is made up of an infinite number of one dimensional lines, a solid is made up of an infinite number of 2 dimensional surfaces stacked next to each other. Again, the direction of the 3rd dimension in relation to the 2nd is that it runs at 90° to it. Before we forget, this 3-dimensional solid exists in space only AND NOT IN TIME! This is a crucial point, as we easily forget that we automatically perceive events that occur in time! In a way, the 3rd dimension is a “snap-shot” of a solid object (e.g. a sphere or a cube) existing outside of time. For it to exist within our world, it needs to be traveling in the 4th dimension i.e. an infinite number of 3-dimensional objects stacked next to each other. The direction of the 4th dimension in relation to the 3rd is that it runs at 90° to it! This may take some time to sink in, but time is a higher dimension of space. Our notion that time is clearly different from the 3 dimensions in space is an illusion, caused by our limited perceptive capabilities.
The idea that animals with highly developed eyes, living in the same environment as humans but perceiving visual information in a completely different way may seem absurd, but there is plenty of evidence in support of this idea.
The evolution of stereoscopic vision in higher primates took place in tropical rainforest canopies, where, for the first time in ages, certain species had little to fear from predators. As a result of this break from tradition, these primates’ facial features and skull shape began to change. Now unbounded from having to keep a wide-angle lookout for predators, they developed stereoscopic vision, enabling them to construct a three dimensional perception of the world around them. Unlike predators who developed stereoscopic vision for pinpointing distances during an attack (and for no other reason!) primates needed it in order to leap from tree to tree whilst avoiding all contact with the dangerous “ground” region of the planet. Maybe as a direct result of this new vision, brain development grew. Or perhaps it was the other way round. I reckon a snowball effect could be a safe compromise to this issue of which came first. The eyeball developed specialized cells called rods and cones and focusing also became possible. This was no doubt to be able to recognize at a distance ripe fruit and other food that grew exclusively in the forest canopy. Tiny details were now perceivable by ever increasingly curious creatures, living in an earthly paradise without a care in the world. Apart from the odd eagle or serpent.
Interestingly, there is no specialized part of the brain responsible for processing stereoscopic vision: it comes from various different regions of the brain. Maybe other neural functions became re-wired in order to evolve as fast as possible: for example, nowadays our sense of smell is basically non-existent!
Amazingly, the percentage of people living today who have problems constructing a stereoscopic view of the world is truly shocking! Only one third of people can see unaided in stereo; one third can learn to see in stereo if the problem is caught early enough and one third of people can never see in stereo! To find out more, please go to http://nzphoto.tripod.com/sterea/3dvision.htm
Another analogy can be drawn from a personal experience with learning how to see computer designed 3-D pictures. Whilst getting drunk in a pub one evening, some friends and I were drawn to several books in which were a whole series of 3-D pictures. If you focus your eyes on the surface of the flat image, you see a complex repeated pattern but no discernable “3-D”image perceivable within this information. Only if you can learn to focus beyond the paper at just the right skew can the brain orchestrate and construct the hidden 3-D image, as half the information is coded in the left hand side of the image and the other half in the right. After five pints of bitter and countless time spent squinting at a meaningless jumble of colour, I slowly started to see a meaningless jumble but with depth, followed by my first ever glimpse of The statue of Liberty in full stereoscopic vision. Once I had made a leap into this new world I could de-code any image within a few seconds of squinting. Another friend with us was unable to learn how to do it , no matter how much he tried (or drank!).
People who have had their vision restored after prolonged blindness have to endure a period of